Antistatic fabrics

ABSTRACT

A non-woven carpet which will not build up electrostatic charges and the process for making it, comprising forming two independent non-woven fabrics of synthetic fibers the fabric which is to constitute the tread surface containing copper fiber and the other being substantially free thereof, superposing said fabrics, and needling said superposed structure to carry fiber including copper fiber from the tread surface fabric into the base fabric layer, the overall content of copper fiber in said carpet comprising about 0.5 to 5 percent by weight of the total fiber content.

ilnited States aterit Bischofi Sept. 17, 1974 ANTISTATIC FABRICS 3,511,740 5 1970 Sanders 161/62 3,582,445 1/1971 Okuhashi.. 161/175 [75] Invent meter Hohensachsen, 3,582,448 1 1971 Okuhashi.. 161/175 Germany 3,669,819 6/1972 Bischoffw 161/155 3 3,690,057 12/1972 Norris .1 57/157 AS [73] Asslgnee' gg hg g 3,713,960 1 1973 Cochran 161 /175 Filedi J 1972 Primary Examiner-Marion E. McCamish [211 App] NO 215 356 Attorney, Agent, or Firm-Burgess, Dinklage &

' Sprung [30] Foreign Application Priority Data 57] ABSTRACT Jan. 16, Germany v 1 A non woven carpet not up electrostatic charges and the process for making it, compris- 2 15428/ g gg ing forming two independent non-woven fabrics of [58] Fieid 154 155 synthetic fibers the fabric which is to constitute the 1 61/175 87 2 tread surface containing copper fiber and the other 2/41 1 6 764/DIG being substantially free thereof, superposing said fab- I rics, and needling said superposed structure to carry fiber including copper fiber from the tread surface 5 6] References Cited fabric into the base fabric layer, the overall content of copper fiber in said carpet comprising about 0.5 to 5 UNITED STATES PATENTS percent by weight of the total fiber content. 2,373,033 4/1945 Kopplin 161/59 3,415,713 12/1968 Smith 161/154 4 013111543 Drawmg Flglres PAIENIEBSEP 1 7 [974 FIG. 1.

FIG. 2.

4 FIG. 3. -i-Ai-EP 3:;

ANTISTATIC FABRICS The invention relates to the manufacture of a nonwoven fabric made from synthetic fibers, in which the electrostatic self-charging of these fibers is prevented.

In recent years the manufacture of non-woven materials made of synthetic fibers has been increasing steadily. One example is the so-called needled mat carpets or floor coverings which may contain polyolefin, e.g. polypropylene, polyester or nylon fibers. With carpet materials such as these, electrostatic charges can be built up merely by walking on them.

Attempts have already been made to treat the synthetic fibers with antistatic preparations. This is also possible with fibers having an active surface, such as polyamide fibers, for example. In the case of polyolefin and polyester fibers, however, this method is unsuccessful, since the preparations do not adhere sufficiently well to the fibers, and after such materials have been walked on for a period of time these preparations are worn away and the undesirable electrostatic charging resumes. Disadvantages also are found in the easier soiling of the floor covering when antistatic preparations are used.

It is accordingly an object of the invention to provide synthetic fiber non-woven fabric suitable for use as carpets which will not build up electrostatic charges and which will retain the property even after prolonged use.

These and other objects and advantages are realized in accordance with the invention by preparing two nonwoven sheets or fabrics, one containing a small amount of copper fiber, superposing the fabrics and subjecting the structure to needling to force some of the copper fibers into and through the fabric which was initially free thereof.

The copper fibers can easily be processed with the others in a carding machine, so that the fiber mat that comes from the card contains the copper fibers uniformly distributed therethrough. This mat containing the copper fibers is then superimposed on the other layer which consists of the same thermoplastic fibers without the addition of copper. Then the two layers of matting are needled together, whereupon the copper fibers in the upper, first layer, which initially lie generally parallel to the plane of the table, are caught by the barbs of the needles and turned athwart their original direction. In this manner it is sought to pull a large number of copper fibers from the upper or tread surface of the needled structure to the lower surface or base.

The invention will be further described with reference to the accompanying drawing wherein:

FIG. 1 is a schematic sectional view through the individual fabrics;

FIG. 2 is a schematic sectional view of the superposed fabrics prior to needling; and I FIG. 3 is a schematic sectional view showing the composite needled carpet.

Referring now more particularly to the drawing, in FIG. 1 there are shown synthetic fiber mats l and 2, fiber mat 1 including copper fibers 3. The two mats are superposed as shown in FIG. 2 and then needled. Thereby many of the synthetic fibers, including most of the copper fibers, are projected downwardly at approximately 90 to the plane of the fabric in bunches 4 which impart mechanical stability to the structure.

If a material such as shown in FIG. 3 is used as a carpet and comes in contact with a grounded floor, dissipation of the electricity is well assured. Since the copper fibers also provide a conductive path between the soles of the shoes of a person walking on the carpet and the grounded underlayment, the person himself is prevented from becoming electrically charged and getting an electric shock upon contacting windowframes, doorknobs etc. The effect is improved further by the use of conductive soles. The needled, copper fibercontaining, non-woven fabrics in accordance with FIG. 3 can be impregnated with binding agents to further improve mechanical strength and resistance to wear. Copper fibers have a toughness and elasticity similar to synthetic fibers, and therefore it is possible to card and needle them without causing breakage of the fibers.

The invention will be further described in the following illustrative example.

EXAMPLE On two carding machines, two polypropylene fiber pile fabrics are produced, each having a weight of 300 grams per square meter; the fiber length is about mm and the denier is about 25. By means of the card, 12 g of copper fibers ofa length of 60 mm and a diameter of 70 microns are worked into one of the two fabrics. Then the fabric containing the copper fibers is laid onto the other fabric and the two are needled. The nonwoven fabric sheet material thus produced will then weigh 612 grams. It is then impregnated with a 40 percent aqueous dispersion of an acrylic ester polymer. After the binder has dried and cured, the non-woven fabric weighs 850 grams per square meter.

As noted, the invention is especially suited for carpets made up of synthetic thermoplastic fibers such as polyolefins, polyester and nylon. The content of copper fiber may vary but generally ranges from about 0.5 to 5 percent by weight of the total fiber content of the carpet. The concentration of the copper fibers adjacent the tread surface of the carpet is higher than at the base, e.g. preferably at least double, and this is desirable since it means there will be more contact between copper fibers and the soles of the shoes of a person walking thereon. Then the flow path of electricity will spread throughout the fabric to be leaked to the ground through many copper fibers, even though much further spaced from one another, due to the network of copper fiber through the whole structure.

The synthetic fibers may be of any standard length e.g. about 40 up to mm or more, and they are generally crimped or otherwise textured. In denier they generally range from about 6 or less up to 70 or more, preferably from about 12 to 40. The copper fibers may vary similarly in length and denier.

It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.

What is claimed is:

l. The process for making a non-woven carpet which will not build up electrostatic charges, said process comprising forming two independent non-woven fabrics of synthetic fibers, the fabric which is to constitute the tread surface containing copper fibers and the other being substantially free thereof, superposing said fabrics, and needling said superposed structure to carry fiber including copper fiber from the tread surface fabtwice the concentration in the base fabric layer half ric into the base fabric layer, the overall content of cophi k per fiber in said carpet comprising about 0.5 to 5 percent by weight of the total fiber content.

2. The process of claim 1 wherein needling is effected 5 to such extent that the concentration of the copper fi- The P Produced y the Process of Claim bers in the tread surface half thickness is at least about 3. The product produced by the process of claim 2. 

2. The process of claim 1 wherein needling is effected to such extent that the concentration of the copper fibers in the tread surface half thickness is at least about twice the concentration in the base fabric layer half thickness.
 3. The product produced by the process of claim
 2. 4. The product produced by the process of claim
 1. 